JPH01294274A - Recording system discriminating device - Google Patents

Abstract

PURPOSE:To discriminate the recording system without being affected by the change of the gain neither the DC drift by discriminating the frequency of a reference part of an information signal. CONSTITUTION:A reproduced FM signal obtained from a magnetic head 3 is amplified by a regenerative preamplifier 4 and is converted to a square wave signal by a waveform shaping circuit 5 and is supplied to a digital counter 6. The digital counter 6 counts input pulses while a gate signal (e) is in the high level, and this counter 6 holds the counted value, which is obtained just before the gate signal (e) goes to the low level, till the next reset pulse. This held counted value is proportional to the frequency of the reproduced FM signal in the period when the gate signal (e) is in the high level, and this counted value is transmitted to a digital comparator 7 at a prescribed timing and is compared with a reference value set by a reference value setting circuit 8 to obtain the discrimination result. Thus, the recording system is discriminated without being affected by the change of the gain neither the DC drift.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a recording method discriminating device for discriminating between a normal format and a high band format.

(b) Conventional technology Japanese Patent Application Laid-Open No. 61-253605 (G11B51027
) discloses a video tape recorder (VTR) that uses the fact that the voltage of a video signal after demodulation differs depending on the deviation ratio of the recording FM signal due to the difference in the format to determine the format by comparing the voltage with a reference voltage. ing.

Q-Angle Problem to be Solved by the Invention However, in the above-mentioned conventional technology, there is a risk that the determination may malfunction due to a change in the gain of the FM demodulator or a drift in the FM demodulator and the DC level detection circuit.

B) Means for Solving the Problems In the present invention, an FM signal is reproduced from a recording medium on which a carrier signal FM modulated by an information signal is recorded, and the frequency of the reproduced FM signal is identified to determine the recording method. It is something to do.

Specifically, the system is determined by measuring the frequency at the timing of the reference part of the information signal (or the synchronization signal part if the information signal is a video signal) and comparing it with the reference.

Alternatively, different frequency components corresponding to the reference portion of the information signal in different systems are extracted from the reproduced FM signal, and the levels are compared to determine the system.

(G) Effect: By directly using the frequency of the reproduced FM signal to determine the recording method, there is no possibility of misjudgment caused by gain fluctuations or drifts of the FM demodulator, etc.

Further, by detecting a frequency signal corresponding to the reference portion of the information signal, a stable discrimination operation can be performed.

(f) Example Hereinafter, the present invention will be described in detail with reference to the drawings.

1 to 6 relate to the first embodiment, with FIG. 1 being a block diagram and FIGS. 2 and 3 being waveform diagrams. Figures 4 to 7 relate to the second embodiment, with Figure 4 being a block diagram, Figure 5,
FIG. 6 is a waveform diagram, and FIG. 7 is a characteristic diagram of the bandpass filter.

All of the embodiments relate to discrimination between a normal recording method and a no-band recording method in an electronic still camera.

An overview of electronic still cameras is given, for example, in "Nikkei Electronics J, July 2, 1984, PP, 80-85. In a normal FM signal in an electronic still camera (normal recording method), the frequency of the sync chip is S
, QMHz, and the deviation is set to 1.5MHz. On the other hand, as a means to improve image quality, it is also conceivable to adopt a biband recording method in which the frequency of the carrier signal is increased and the range of deviation is widened. For example, it is conceivable to set the sync chip frequency to 7 MHz and the deviation to 2.0 MHz.

When such different recording systems exist, it is desirable that the system be automatically determined during playback.

In Figure 1, (1) is a magnetic disk, (2) is a PG yoke for detecting rotational position (for detecting the position of a vertical synchronization signal and synchronizing), (3) is a magnetic head, (4) is
is a reproduction preamplifier, (5) is a waveform shaping circuit, (6) is a digital counter, (7) is a digital comparator, (8)
) is the reference value setting circuit, (9) is the PG sensor, α0 is the PG
An amplifier, αD is a waveform shaping circuit, ■ is a timing control circuit, αJ is a reproduction RF (FM) signal output terminal, and α is a determination result output terminal.

The magnetic disk (1) is driven by a drive means (not shown).
It is rotated at 60 rpm. Its rotational phase is PG
It is detected by the action of the yoke (2) and the PG sensor (9) (Fig. 2 (a)), and is amplified by the PG amplifier dish (Fig. 2 @
), the waveform is shaped (Fig. 2 (φ). This PG pulse (
The timing control circuit (output of the waveform shaping circuit α1) generates a reset pulse (see Figure 2 (Φ
) and a gate signal (FIG. 2(e)) are generated and output.

The reproduced FM signal obtained from the magnetic head (3) (Fig. 2 (
0) is amplified by the reproduction preamplifier (4) and sent to the terminal (131
The signal is then supplied to an FM demodulator (not shown). On the other hand, the reproduced FM signal (0 is a rectangular wave signal (
2(g)) and supplied to the digital counter (6).

The counting operation of the digital counter (6) is controlled by a reset pulse (ψ) and a gate signal (e), and the counting operation is controlled by a reset pulse (ψ) and a gate signal (e).
During the period when the gate signal (e) is at the H level, input pulses (for example, the rising edge of a rectangular wave signal) are counted, and the count value immediately before the gate signal (e) goes to the L level is held until the next reset pulse.

This held count value is proportional to the frequency of the reproduced FM signal during the period when the gate signal (e) is at H level (this means that the frequency is measured).

This count value is transmitted to a digital comparator (7) at a predetermined timing, and compared with a reference value set by a reference value setting circuit (8) to obtain a determination result.

According to the electronic still camera standard, the interval between the PG pulse and the vertical synchronization signal of the video signal recorded on the magnetic disk is 7H (±1H) (H is the horizontal synchronization period) (the vertical synchronization signal is delayed).

FIG. 6 shows an enlarged view of the vicinity of this vertical synchronizing signal. As is clear from the figure, the reset pulse (FIG. 6(C)) is a signal obtained by delaying the PG pulse (FIG. 6(A)) using a monomultiplier or the like. Gate signal (see Figure 3)
) is further delayed than this reset pulse 9.

The delay time from the PG pulse (a) is set to 7 to 9.5H, and the pulse width is 0.5H. That is, the gate signal is set to be included in the vertical synchronization signal period (H minute) of the video signal.

Considering that the period between the PG pulse and the vertical synchronization signal varies by ±1H1H, it is desirable that the gate signal () be set in the period from 8H to 9H from the PG pulse (a). By extending the H level period by 0.5H, one equivalent pulse is always included, so there is no problem in comparison. Even if the gate signal width is set to 1H, two equivalent pulses will always be included, but in this case, when the interval between the PG pulse and the vertical synchronization signal deviates,
There is a possibility that the signal may deviate from the vertical synchronization signal period.

It is fine if the reset pulse λ (c) is at the timing before the gate signal), but is it the reset pulse? Since the method determination is invalid during the period between (now and the gate signal), it is preferable that it be immediately before.

Next, the operation will be explained. -times counting operation (discrimination operation) is performed for every seven revolutions of the magnetic disk (1). In other words, the digital counter (6) is reset by the reset pulse e, and the gate signal for the next 0.5H is
During the level, a counting operation is performed. As explained earlier, in the normal recording method, the frequency corresponding to the sync chip is 6 MHz, so the count value is about 190, and in the high band recording method, the frequency corresponding to the sync chip is 7 MHz, so it is about 250. , it is thought that the counted value will not deviate significantly from the above value).

Therefore, the reference value of the reference value setting circuit (8) is set to r
If 220J is set, the recording method can be determined based on the output level (H level or L level) of the digital comparator (73).

In other words, when the count value is about 190, it is smaller than the standard value,
An L level output is obtained, indicating that the normal recording method is used. On the other hand, when the count value is about 250, an output of H level, which is larger than the reference value, is obtained, indicating that the high band recording method is used.

In the first embodiment, the sync tip level portion of the vertical sync signal portion is selected, but the sync tip portion of the horizontal sync signal or the pedestal portion of vertical or horizontal blanking may be used. In addition to PG pulses, it is also possible to use demodulated synchronization signals as a standard for creating gate pulses (however, it is assumed that the demodulation operation can be realized regardless of the method. If not, use PG pulses) is better).

Furthermore, the information signal may be not only a video signal but also an audio signal or a data signal. At this time, there must be a reference portion such as a blanking period of the video signal. Further, as in the above example, unless the deviations of the two systems are close to each other, the timing of the gate signal may be arbitrarily determined (the gate signal pulse width is constant).

Next, a second embodiment will be explained. In FIG. 4, the same parts as in FIG. 1 are given the same reference numerals, and their explanation will be omitted. The filter is a bandpass filter with center frequency f1, α'
7) is a bandpass filter with center frequency f2, (1εα
The level detection circuit (2) is a voltage comparator, and the result holding circuit (D-type flip-flop) (2) is a trigger pulse generation circuit.

The center frequencies f+ and fl are set to frequencies corresponding to the sync tips in the two systems. In other words, f t=
6. [ ] MHz, f 2 = 7.7 MHz (see Figure 7).

Therefore, in the circuit shown in FIG. 4, the frequency components fl and fl are extracted from the reproduced FM signal, and after level detection, the levels are compared. Then, this comparison result is held by a trigger pulse (holding port fill at the timing shown in FIG. 5 (Φ)). The timing of this trigger pulse (d) is set to the period of the sync tip level of the vertical synchronizing signal, as shown in FIG.

Therefore, if the fr component is large at the timing of the trigger pulse (ψ), the H level is held, indicating normal recording. Conversely, if the fl component is large, the L level is held, indicating high band recording. It is shown that

In addition, even if the vertical synchronization signal position fluctuates,
There is no change in the fact that the trigger pulse (ψ) exists within the vertical blanking period, and the pedestal frequency (6.5 MHz
, 8.3 MHz), there will be no problem in discrimination by selecting a band around α of the bandpass filter.

Similarly to the first embodiment, the second embodiment can be modified in various ways. In addition, in any of the embodiments, the VTR
Needless to say, it can be applied to

(g) Effects of the Invention As described above, according to the present invention, the recording method can be determined without being affected by gain changes or DC drift, and therefore the effects are great.

[Brief explanation of the drawing]

1 to 6 relate to the first embodiment, with FIG. 1 being a block diagram and FIGS. 2 and 3 being waveform diagrams. 4 to 7 relate to the second embodiment, in which FIG. 4 is a block diagram, FIGS. 5 and 6 are waveform diagrams, and FIG. 7 is a characteristic diagram of a bandpass filter. (6)...Digital counter, α6) (1η...Band pass filter, 181 concave...Detection circuit, ■...
voltage comparator.

Claims (3)

[Claims] (1) A recording method identification device that identifies recording methods in which recorded FM signals have different frequencies during reproduction, and is characterized in that it identifies the frequency of a reference portion of an information signal. (2) The recording method discriminating device according to item 1, which measures the frequency at a timing corresponding to the reference portion of the reproduced FM signal, and compares the measurement result with the reference to make the discrimination. (3) The recording method discriminating device according to item 1, which extracts different frequency components corresponding to the reference portion in different recording methods from the reproduced FM signal and compares the levels thereof.